The present invention relates to a method of and an apparatus for treating refuse. More particularly this invention concerns a system for the nonpolluting disposal of refuse and the recovery of valuable recyclable constituents from refuse.
It is known to separate standard household refuse into a light organic fraction and a heavy hard fraction. This light fraction is comprised mainly of paper products, textiles, and the like and the heavy fraction is constituted of metal objects, stone, and otherwise very dense or wet objects. A common procedure is to comminute both fractions and feed the comminuted heavier fraction onto a grate in a combustion chamber. The comminuted light fraction is either blown directly or stored and then blown into the combustion chamber.
In such a system the principal combustion therefore takes place on the grate in the combustion chamber. The comminuted fine fraction which is blown in above the main fire on the grate is simultaneously combusted.
Such an arrangement has several disadvantages. First of all the grate tends to wear very rapidly, as it is subjected to considerable mechanical wear and considerable heat. In particular much refuse when burned produces corrosive acids which eat away even the most heavily constructed combustion grate. For this reason it is common practice in most such systems to provide several combustion chambers in parallel so that it is possible to shut one down at any given time and service it. Such servicing is required frequently and is expensive.
Furthermore, in such an arrangement the combustion of the refuse on the grate is often inadequate. The comminuted heavy fraction is frequently quite moist so that it cannot be burned completely. Thus, gases are produced which are themselves not sufficiently combusted so that it is necessary to provide a very expensive filtering arrangement at the outlet of this system in order to treat the noxious gases so produced.
In addition, such systems frequently are set up so that all of the refuse delivered to them must be treated immediately. Since it is common practice to use the heat created by such systems for the generation of electricity, it is therefore impossible to operate the systems at a higher rate during peak electricity-consumption hours.
It is also known in such systems to feed in wet sludge from a sewage-treatment installation. The intake rate of such sludge is normally dependent on the temperature in the combustion chamber, more sludge being fed in when the temperature is high and less when the temperature is low. Such an arrangement has the disadvantage that the wet sludge causes considerable generation of water vapor inside the combustion chamber. The water vapor combines with any acids driven out of the burning refuse so as to increase the pollution problem, and simultaneously increases the relative inertness of the atmosphere inside the combustion chamber. As the amount of water vapor increases the generation of carbon monoxide and other poisonous gases will also increse due to insufficient combustion, so that once again the system generates considerable pollution.